Main Panel or Sub-panel by code

[hardworker]

A commercial building has a 400amp single phase main panel. Another electrician installed a 200amp single phase "sub" panel from this main panel.

The 400amp main panel had no available spaces for the 200amp breaker, so he tapped the two hot conductors on the line side of the 400amp breaker in the factory supplied terminals. (this panel had two extra taps) The neutral conductor was tapped on the neutral bar of the main and the ground conductor was tapped on the ground bar of the main panel.

The two hot conductors are upstream from the 400amp breaker and technically speaking they are not drawn from the main.

The neutral and the ground are on the main.

Is this 200amp panel a sub-panel or a second main panel?

The other electrician said it was a second main, therefore on the 200amp panel, the neurtrals must be bonded to the grounds as opposed to isolated.

The other electrician did a load calculation and all is well within limits.

What is your determination of this and what does code say about this?

 

[PEDRO ESCOVILLA]

i'd call it illegal. dangerous at best. are the feeders supplying the first 400 amp main large enough for 600 amps ? sounds fishy to me. maybe i'm wrong, it doesn't sound right. i wouldnt call is a second "main" or a sub panel. its not a subpanel because its not fed from a breaker, its fed straight from the feeders that feed the 400 ( if i read you correctly). a main be fed from/through a seperate meter or transformer, this has neither. did it pass inspection?

 

[chris kennedy]

It would be main 2 of 2 but the EGC sounds like a parallel grounded conductor.

 

[hillbilly1]

Several questions, is the 400 amp panel service equipment? Or is being feed from another main that is the service equipment? If it is the service equipment, then it would be a second main, if it is not, then it's a sub panel. Also if it is service equipment, are the service conductors large enough for a 600 amp service? If it is not service equipment, then the tap rule would apply, and the ocp would not matter other than limiting the minimum size of the tap.

 

[chris kennedy]

are the feeders supplying the first 400 amp main large enough for 600 amps ?

are the service conductors large enough for a 600 amp service?

Check 230.42.

 

[chris kennedy]

Sorry, and 230.90(A) ex 3.

 

[hillbilly1]

Sorry, and 230.90(A) ex 3.

That answers that question then, because of more than one main, and if the calculated load qualifies, then yes.

 

[hardworker]

The 400amp is service equipment. It comes directly from the meter outside the building.

A load calculation was done and the total load is well below the 400amps. The feed conductors are ample.

What is the situation about a paralell ground?

Should the ground bar and neutral bar be bonded in the sub?

Do you see any problems other than load?

 

[fmtjfw]

Unless the second panel is a fire pump you may have another problem:

Are the panels side by side?

230.72 Grouping of Disconnects.
(A) General. The two to six disconnects as permitted in
230.71 shall be grouped. Each disconnect shall be marked
to indicate the load served.
Exception: One of the two to six service disconnecting
means permitted in 230.71, where used only for a water
pump also intended to provide fire protection, shall be permitted
to be located remote from the other disconnecting
means. If remotely installed in accordance with this exception,
a plaque shall be posted at the location of the remaining
grouped disconnects denoting its location.

 

[fmtjfw]

The second panel is not a sub. There are two service panels. Each is to be connected to the GEC and each is to be bonded to the Neutral. see 250.24(B).

 

[hardworker]

The panels are side by side within 24 inches of each other.

When you say "each to be connected to the GEC" are you saying the 2nd main can be connected to the GEC of the 1st main, that has a ground rod and ground to a water line? The 2nd panel does not need its own ground rod and water line ground.

Do I understand correctly?

 

[chris kennedy]

What is the situation about a paralell ground?

The neutral conductor was tapped on the neutral bar of the main and the ground conductor was tapped on the ground bar of the main panel.

You have a main bonding jumper in both the 400 and 200. The wire type EGC between the two is unnecessary and IMO a violation of 250.6(A). Now even with the EGC removed, if the installer used a conductive metallic wiring method the two you will have a similar situation. Nothing you can do about that.

 

[kwired]

The 400amp is service equipment. It comes directly from the meter outside the building.

A load calculation was done and the total load is well below the 400amps. The feed conductors are ample.

What is the situation about a paralell ground?

Should the ground bar and neutral bar be bonded in the sub?

Do you see any problems other than load?

There is no sub panel, both are service equipment and must be grouped together - which you indicate they are, if the calculated load is less than the incoming conductors this is a permitted installation. Each service disconnect enclosure must be connected to the grounding electrode system.

 

[RICK NAPIER]

if the installer used a conductive metallic wiring method the two you will have a similar situation. Nothing you can do about that.

That has always bothered me but to be honest I have not seen a lot of issues arise because of this parallel path on a service. I was just wondering if any of you out there have seen problems with the parallel path created when using a conductive metallic wiring method on a service? The most common example would be metal conduit between the meter and the main.

 

[Cow]

..........

 

[chris kennedy]

I was just wondering if any of you out there have seen problems with the parallel path created when using a conductive metallic wiring method on a service?

Nope.